Devices for starting a double action free piston engine having a single cylinder



Dec. 19, 1967 P. PANHARD 3,353,556

' DEVICES FOR STARTING A DOUBLE ACTION FREE PISTON ENGINE HAVING A SINGLE CYLINDER Filed March 17, 1966 .2 Sheets-Sheet 1 Page Pom/5 a rd ATT0RNEY5 Dec. 19, 1967 P. PANHARD 3,358,656

' DEVICES FOR STARTING A DOUBLE ACTION FREE PISTON ENGINE HAVING A SINGLE CYLINDER Filed March 17, 1966 2 Sheets- Sheet 2 lNVEN TOR 8% SS Q 19 pdM/ dn ha rc/ BY United States Patent DEVICES FOR STARTING A DOUBELE ACTION FREE PISTQN ENGINE HAVING A SINGLE CYLINDER Paul Panhard, Paris, France, assignor to Societe Anonyme Andre Citroen, Paris, France, a society of France Filed Mar. 17, 1966, Ser. No. 535,198

Claims priority, application France, Mar. 23, 1965,

12 Claims. 201. 123-46) The present invention relates to devices for starting an internal combustion engine including a free piston forming inside a cylinder a partition between two combustion chambers. The invention is more especially concerned with a device of this kind for an engine into combustion chambers of which fuel is injected directly through means responsive to the position of the free piston in its cylinder.

The chief object of the present invention is to provide a starting device of this kind which is better adapted to meet the requirements of practice than those existing at the present time and in particular which includes no mechanical connection with the free piston.

According to the present invention, this device comprises, on the one hand, means for admitting air under pressure into one of the combustion chambers of the internal combustion engine (hereinafter called first chamber) and for placing the other of these chambers (hereinafter called second chamber) in communication with the atmosphere, in such manner as to bring the free piston initially into its stroke end position for which the volume of the first chamber is maximum, whatever be the position of this piston before the starting of the engine, and, on the other hand, means for subsequently admitting air under a high pressure into the second chamber so that the piston performs a compression stroke with respect to the first combustion chamber which is then closed and filled with a fuel and air mixture, which produces combustion or explosion in said first chamber, after which the engine works normally without any action of the above mentioned means.

Preferred embodiments of the present invention will be hereinafter described with reference to the appended drawings, given merely by way of example, and in which: FIG. 1 is an axial sectional view of a free piston single cylinder internal combustion engine provided with a starting device made according to a first embodiment of the invention;

FIG. 2 is a view similar to FIG. 1 of an internal combustion engine provided with a starting device made according to a second embodiment of the invention;

FIG. 3 is a detail view of an element of thedevice of FIG, 2 in another position of operation.

The starting device according to the present invention illustrated by the drawings is for use with a free piston single cylinder internal combustion engine driving a hydraulic transmission pump or, generator, for instance of the type described in the U.S. patent application No. 512,629 of Dec. 9, 1965.

The internal combustionengine illustrated by the drawings comprises a free piston 1, the two opposed faces 2 and 3 of which limit in a common cylinder 6 two respective combustion chambers 4 and 5. Piston 1 is provided on its opposed sides with rods 7 and 8 which are slidable in the heads of cylinder 6 These rods 7 and 8 may act as pistons or plungers of reciprocating pumps the whole of which constitutes the generator of a hydraulic transmission. Said rods 7 and 8 may further control the injection of fuel into chambers 4 and alternately, as described in the U.S. patent application No. 514,731 of Nov. 19, 1965.

As the above mentioned hydraulic transmission and the fuel injection system have no influence upon good under- 3,358,656 Patented Dec. '19, 1967 standing of the invention, they are not described here. FIG. 1 merely shows inlet pipes 9 and delivery pipes 10, the ports of which are directly controlled by piston 1.

In such an internal combustion engine, there is no mechanical connection between piston 1 and the outside, rods 7 and 8 ending inside the above mentioned reciprocating pumps. It is therefore very difficult to have the starting device operated by the movement of the piston.

The starting device according to the present invention includes, as shown by FIG. 1:

On the one hand, first means for admitting air under pressure into the first chamber 4 and for connecting the second chamber 5 with the atmosphere, so as first to bring free piston 1 at the stroke end of which the volume of the first chamber 4 is maximum (said stroke end being indicated by the dot-and-dash lines 2a and 3a which represent the corresponding position of piston faces 2 and 3), and

On the other hand, second means for subsequently charging air under high pressure into the second chamber 5, whereby piston 1 is given a compression stroke With respect to the first chamber 4 which is then closed, which produces combustion, or explosion, in said first chamber 4 owing to the fuel that has been fed thereinto during the first compression stroke, after which the engine works normally, without any action of the means which have been above mentioned.

The first means comprise a first compressed air chamber 11 adapted to be connected, through a distributing device 12 represented by a cock in FIG. 1, on the one hand to a pipe 13 leading to the first chamber 4 through the intermediate of an automatic valve 14, and, on the other hand to a conduit 15 leading to a pneumatic device 1718 capable of opening a valve 16 adapted to place second chamber 5 into communication with the atmosphere. Valves 14 and 16 are normally held in the closed positions thereof by respective springs 14a and 16a and by the pressure existing in chambers 4 and 5, but valve 14 is arranged to let pass into chamber 4 the air flowing through distributing device 12 from chamber 11, no counter pressure existing at this time in chamber 5. Pneumatic device 17-18 comprises a piston 17 rigid with valve 16 and housed in a cylinder 18 into which pipe 15 opens, spring 16a acting upon valve 16 against the action of the pressure in cylinder 18. The connection of the second chamber 5 with the atmosphere is obtained in a manner which will be hereinafter explained.

The second means above referred to comprise a second compressed air chamber 19 connected with the second combustion chamber 5 through a pipe 20 and an automatic valve which is constituted with the pneumatically control valve l'dabove referred to. Consequently, this valve 16, which remains closed during the normal operation of the engine, same as valve 14, is adapted to open not only when air under pressure coming from chamber 11 is ad'mitted'into cylinder 18, to permit the emptying of chamber 5, but also when air under pressure coming from chamber 19 through pipe 20 is directed onto the external face of valve 16 so as to be admitted into chamber 5.

In order to enable pipe 20 either to connect combustion chamber 5 with the atmosphere or to fill said chamber with air under pressure from chamber 19, there is provided between the outlet conduit 21 of said chamber 19 and pipe 20, a slide valve 22 movable in a cylinder 23 and urged by spring 24 toward the position illustrated by FIG. 1, where said slide valve 22 closes conduit 21 and places pipe 20 into communication with the atmosphere through passages 22a provided in said slide valve 22 and cooperating with the end 22a of pipe 20, and through an orifice 25 provided at the end of cylinder 23. When chamber 19 is placed in communication with conduit 21 in the manner hereinafter described, the compressed air from said chamber 19 pushes slide valve 22 against the action of spring 24 (i.e. toward the left of FiG. 1) which, on the one hand, shifts passages 22a away from the end 20a of pipe 29 so that said pipe is no longer in communication with the atmosphere, and, on the other hand, connects conduit 21 with the end Zita of pipe 20 so that chamber 19 is then in communication with chamber 5 owing to the opening of valve 16.

Chambers 11 and 19 are located in a common cylinder 26 where they are separated from each other by a piston 27 slidable in said cylinder 26 and adapted to come into contact with an abutment 28, the volume of chamber 11 being then maximum but still much smaller than that of chamber 19, although the latter is then minimum.

Chamber 11 is connected with a compressor 29 through a delivery pipe 30' provided with a check valve 30a.

Between chambers 11 and 19 there is provided a check. valve 31 housed in piston 27, whereby air can flow only from chamber 11 to chamber 19.

Between chamber 19 and conduit 21 there is provide a check valve 32 cooperating with a seat 33 and controlled by piston 27 in such manner that check valve 32 is closed (as shown by the drawing) when piston 27 is applied against its abutment 28, but that said check valve 33 is opened when piston 27 reaches a given limit position at a distance from abutment 28.

In order to operate check valve 32, there is provided a rod 34 extending longitudinally in chamber 19 and pulled by piston 27 to move check valve 32 away from its seat 33. For this purpose, a head 34a carried by the end of rod 34 cooperates with a shoulder 27a provided in piston 27. Check valve 32 is adapted to be closed by a spring 35 when piston 27 is applied against abutment 23, this spring 35 being interposed between head 34a and piston 27.

Although compressor 29 has been shown as having a single stage it generally includes two stages, so as to be able to fill chamber 19 with air at a suificient pressure (preferably averaging 16 kgs./cm.

The starting device of FIG. 1 works as follows: The operation includes three successive steps, to wit the filling of chambers 11 and 19; a preparatory stroke of piston 1 (toward the left of FIG. 1); and the starting stroke (toward the right of FIG. 1).

Concerning the filling of chambers 11 and 19, when compressor 29 is started, it delivers air through conduit 30 past check valve 30a into chamber 11, distributing device 12 being closed. As the spring 31a of check valve 31 produces a pressure drop of the air flowing through said check valve 31, piston 27 moves toward the left until it is stopped by its abutment 28, which causes check valve 32 to be applied against its seat 33 through rod 34. Co. press or 29 fills up chambers 11 and 19 with compressed air marine pressure therein reaches a given value (for instance 16 kgsJcrnF). At this time, compressor 29 is placed out of action in a canner which will be hereinafter explained.

The preparatory stroke of piston 1 is started by opening distributing device 12. The air compressed in chamber 11 passes both into conduit (opening valve 16 and placing chamber 5 into communication with the atmosphere through pipe 20, passages 22a and orifice 25) and into conduit 13 (admission of air into chamber 4). Piston 1, whatever be the position in which it was initially, is pushed toward the left of FIG. 1 into the position diagrammatically illustrated at 2a, 3a, that is to say until the air coming from chamber 11 escapes through the ports of the delivery pipe 10 of chamber 4 then uncovered by piston 1. The pressure in chamber 11 then drops to atmospheric pressure. The same is true of cylinder 18 and valve 16 closes. Chamber 19 remains closed by check valve 32 and the pressure therein has been reduced only to a small extent (its volume being considerably greater than that of chamber 11) by the displacement of piston 27 toward the right. Piston 27 moves toward the right and, at the end of its stroke, opens valve 32.

The starting stroke of engine piston 1 then begins automatically. The air that escapes from chamber 19 through outlet conduit 21 first pushes slide valve 22 toward the left against the action of spring 24. As a consequence, on the one hand, pipe 20 is cut off from discharge orifice 25 and, on the other hand, conduit 21 is placed in communication with pipe 20. The air coming from chamber 19 then flows through pipe 20, lifts check valve 16 and enters combustion chamber 5 strongly pushing piston 1 toward the right from the piston indicated at 242-341. The engine can then work by itself, valves 14 and 16 remaining then permanently closed.

Once the engine has been started, distributing device 12 is closed. Slide valve 22 moves back toward the right under the action of its spring 24. Compressor 29 is started at the suitable time and fills chambers 11 and 19 with compressed air, the displacement of piston 27 toward the left closing back check valve 32.

By adjustment of the maximum admissible pressure in chamber 19 it is possible to give piston 1 a thrust toward the right greater than that it undergoes under normal working conditions under the effect of explosion or combustion in chamber 5, which has for its effect, when the engine is started, to increase the stroke of piston 1 and therefore to reduce the clearance space in chamber 4 and therefore to increase the compression, which facilitates ignition.

Contrary to engines including flywheels, which cannot rotate at a speed greater than -180 revolutions per minute at the time of starting, the thrust imparted to piston 1 toward the right of FIG. 1 gives it a very high speed owing to its small mass, such a speed cor-responding without difliculty to 2800 cycles per minute for the engine, which ensures ignition of the fuel in the most unfavorable cases.

It should also be noted that, during the two first strokes of piston '1, the gaseous fluid admitted into combustion chambers 4 and 5 consists of pure air (fuel being of course added at the ends of the compression strokes) without necessity of any scavenging since, for these two movements, piston 1 has been moved by the air contained in chambers 11 and 19.

It has been stated that the compressor 29 of FIG. 1 is placed out of action when chambers 11 and 19 are filled with air at a given pressure (for instance 16 kgsjcrn This canbe obtained either by means of a compressor having a substantial dead space or including a movable auxiliary piston (the compressor working without feeding air but under the maximum delivery pressure as soon as chambers 11 and 19 are filled), or by means of a compressor having a very small dead space and provided with a pneumatic disconnector device (the compressor then turning at atmospheric pressure as soon as chambers 11 and 19 have been filled with air compressed to the desired pressure).

This last solution is illustrated by FIG. 2, where the pneumatic disconnector, inserted in delivery pipe 30, is designated as a whole by reference numeral 36. The elements of FIG. 2 which are identical to those of FIG. 1 are designated by the same reference numbers.

'Disconnector 36 comprises three chambers 37, 38 and 39. Chamber 37 is connected with the upstream portion of delivery pipe 30. Chamber 38 is connected with the discharge pipe 40 of compressor 29. The third chamber, 39, is connected with the downstream portion of delivery pipe 30. The orifice through which pipe 4!) opens into the atmosphere is designated by 41a.

The three above mentioned chambers, to wit 37, 38 and 39 communicate two by two in the following manner:

Chambers 37 and 39 are connected together by a pipe 41 provided with a check valve 42.

Upstream chamber 37 and intermediate chamber 38 communicate together through an orifice 43 controlled by check valve 44 adapted to be opened, against the action of a spring 45, by a piston 46 slidable in intermediate chamber 38 and arranged in such manner as to leave orifice 43 always in communication with discharge pipe 40.

Intermediate chamber 38 and downstream chamber 39 communicate together through an orifice 4-7 controlled by a check valve 48 adapted to be opened by a piston 50 against the action of a spring 49 acting upon said piston 54 so as to urge it toward an abutment 51. This piston 50 is arranged to always leave pipe 41, orifice 47 and the downstream portion of delivery pipe 30 free to communicate together. Reference numeral 38a designates the portion of chamber 38 limited by piston 46 and which communicates with orifice 47.

Therefore it will be seen that the pressure existing in compressed air chamber 11 is always applied to piston 50 and urges it upwardly against the action of spring 49, the latter being determined to yield to the maximum pressure chosen for compressed air chambers 1'1 and 19, thus opening orifice 47. It will be further seen that orifice 43 remains closed as long as piston 46 is not subjected, on the face thereof opposed to check valve 44, to an air pressure determined by the opening of orifice 47.

Disconnector 36 works as follows:

Compressor 29 being in operation, it feeds compressed air into compressed air chamber 11 through the upstream portion of pipe 30, chamber 37, pipe 41, chamber 39 and the downstream portion of pipe 30. When the maximum pressure has been reached in compressed air chamber 11, piston 50 is pushed away from its abutment 51 against the action of spring 49 and causes check valve 48 to open orifice 47. The air compressed at this pressure is admitted into the volume portion 38a of chamber 38 and pushes down piston 46 which suddenly opens orifice 43 by means of check valve 44. Compressor 29 then feeds compressed air to the atmosphere through the upstream portion of pipe 30, chamber 37, orifice 43, chamber 38, discharge conduit 40 and orifice-40a. Check valve 42 prevents compressed air chamber 11 from emptying; piston 50 is pushed back by its spring 49 against its abutment 51 and check valve 48 closes back, entrapping in volume portion 38a air at the maximum pressure that has been chosen (16 kgs./cm. I

If the pressure in compressed air chamber 11 drops below the value for which spring 49 has been chosen, the pressure in chamber 38a becomes greater and lifts check valve 48. Thisenables spring 45 to lift check valve 44 and to close orifice 43. Compressor 29 ceases to feed compressed air toward discharge conduit 43 but instead of this, it feeds air toward compressed air chamber 11 and consequently air chamber 19.

[Compressor 29 can work permanently, but it is more advantageous to combine it with a starting central member in'such manner that when said member is in action, it first starts the compressor and then, when the desired pressure has been reached in compressed air chambers 11 and 1-9, automatically causes distributing device 12 to open and then stops the compressor, the distributing device then closing automatically.

The starting control member is advantageously arranged in' such manner that, when itis actuated, it exerts a resilient thrust upon a valve 52 mounted in discharge pipe 40, 'a pipe 53 branching olT from discharge pipe 40 upstream of said valve 52 so as to act pneumatically upon distributingdevice 12.

As shown by FIGS. 2 and 3, said control member consists of a push-button 54 rigid with a piston 55 movable in a cylinder 66. Said cylinder 56 carries the seat 57 of valve 52 and is'provided with the discharge orifice 40a. This orifice 40a is located in such manner that it is closed by piston 55 when push-button 54 is depressed as shown by FIG. 3. In this position, said push-button 54 is held by two metal balls 58 urged by springs 59 into a groove formed by a metal ring 60 carried by piston 55. Piston 55 and cylinder 66 are made of an insulating material. In

order to enable push-button 54 to exert a resilient thrust upon valve 52, there is interposed between these two elements a spring 61 exerting a pressure substantially smaller than that of spring 49, for instance of 3 or 3.5 kgs./cm. A spring 62 tends to push back button 54 but its strength is such that balls 58 cannot be retracted by the mere thrust of said spring 62 but by the sum of this thrust and of the air pressure acting on piston 55 when valve 52 is open.

Springs 59, balls 58 and ring 60 form an electric contactor inserted in the feed circuit 63 of an electric motor 64 adapted to drive compressor 69, in such manner that this motor 64 is fed with current when button 54 is depressed (FIG. 3) but ceases to be fed with current when button 54 has been pushed back as above stated and as illustrated by FIG. 2.

Finally use is made of a distributing device 12 adapted to be opened under the effect of the air under pressure fed thereto through pipe 53 and to be automatically closed after the period of time necessary for the discharge of the air in compressed air chamber 11 into the engine chamber 4 so as to bring engine piston 1 into the position diagrammatically illustrated at 2a-3a.

This distributing device 12 includes three spaces or chambers 65, 66, 67. Space 65 communicates with pipe 53 through a check valve 68 and a leak passage 69 of small cross section mounted in shunt with check valve 68. Space 66 communicates with the portion 13a of pipe 13 which starts from compressed air chamber 11. Space 67 communicates with the portion 13b of pipe 13 which opens into the chamber 4 of the engine. In space 55 there is slidably mounted a piston 70 adapted to push, against the action of a spring 71, the rod 72 of a check valve 73 cooperating with an orifice 74 formed in a partition provided between spaces 66 and 67. Said check valve 73 is urged toward its closed position by a spring 75. Rod 72 is provided with a leak channel 76 extending between space 67 and the portion 65a of space 65 located on the other side of piston 70 from the outlet of pipe 53. Leak channel 76 is closed when piston 70 bears against the end of rod 72.

The starting device shown by FIGS. 2 and 3 works in the following manner.

When push-button 54 is depressed (position of FIG. 3) two cases may occur. Either chambers 11 and 19 are full of air at the desired pressure or they are not.

In the first case, check valve 44 is open, since discon nector 36 has worked in the manner above described with reference to FIG. 2. Electric motor 64 is started by the closing of contactor circuit 59, 58, 60 and compressor 29 feeds air under pressure which flows out through discharge conduit 40. Valve 52 loaded byspring 61 is closed as long as the pressure in pipe 53 does not reach the force of spring 61 (from 3 to 3.5 kgs./cm. in the example described). Then it opens when this pressure is reached. As soon as the pressure in pipe 53, and consequently in space 65, appropriately reaches said value, piston 70 is pushed toward the right hand side of FIG. 2 and opens check valve 73 against the action of spring 75. This causes air to flow from compressed air chamber 11 into the combustion chamber 4 of the engine (preparatory step before starting). At the same time, due to the opening of valve 52, the air under pressure (from 3 to 3.5 kgs/cm?) fed. through conduit 40 acts upon piston 55, pushes back balls 58 and cause push-button 54 to project outwardly. Circuit 63 is cut off and electric motor 64 stops. I

Check valve 73 remains open during the time taken by piston 70, pushed by spring 75 and 71, to drive out the air from chamber 65 through leak channel 69, this time being adjusted so that the compressed air admitted into the compression chamber 4 of the engine has been able to push piston 1 into the preliminary position shown at 2a-3a.

At the end of its rearward movement, piston 70 permits check valve 73 to close orifice 74 and the air contained in pipe 15 leading to cylinder 17 escapes through leak passage 76. Valve 16 closes. The second step in the starting of the engine takes place in the manner described with reference to FIG. 1, distributing device 12 then having no action.

In the second case (chambers 11 and 19 being not sufficiently filled with air), the check valve 44 of disconnector 36 is closed. Compressor 29 supplies air under pressure to chambers 11 and 19 through pipe 30. When chambers 11 and 19 are filled with air at the desired pressure, valve 44 opens, as explained with reference to FIG. 2 and the situation is the same as in the first case.

It will be understood that the above described starting device works without mechanical connection with piston 1 and in a reliable manner whatever be the position in which said piston has precedingly stopped.

In a general manner, while the above description discloses what are deemed to be practical and efiicient embodiments of the present invention, said invention is not limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the invention as comprehended within the scope of the appended claims.

What I claim is:

1. In an internal combustion engine including a cylinder, a single piston freely slidable in said cylinder dividing it into two variable volume combustion chambers, a first one and a second one, said cylinder being provided with discharge ports to be cleared by said piston when the volume of each of said combustion chambers is maximum, a starting device which comprises, in combination,

first means for feeding air under pressure into the first combustion chamber and for connecting the second combustion chamber with the atmosphere, whereby said piston is pushed in the direction from said first combustion chamber toward said second combustion chamber into the position thereof for which said first combustion chamber has its maximum volume, and

second means, responsive to a displacement of said piston in said direction clearing said discharge ports, for feeding air under high pressure into said second combustion chamber whereby said piston is made to perform a compression stroke with respect to said first chamber.

2. A starting device according to claim 1 wherein said first means include a first compressed air chamber,

a distributing device having its inlet communicating with said first compressed air chamber,

two pipes, a first one and a second one, the first one communicating with the outlet of said distributing device and the second one communicating with the I first one,

said first pipe leading to said first combustion chamber,

a check valve in said first pipe opening toward said first chamber,

valve means for connecting said second combustion chamber with the atmosphere, and

a pneumatic device operative by compressed air from said second pipe for opening said last mentioned valve means.

3. A starting device according to claim 2 wherein said second means include a second compressed air chamber, and

automatic valve means for connecting said second compressed air chamber with said second combustion chamber.

4. A starting device according to claim 2 wherein said second means include a second compressed air chamber,

the valve means for connecting said second combustion chamber with the atmosphere including a slide valve element operative by the air pressure in said second compressed air chamber to close the communication between said second combustion chamber and the atmosphere while placing said second compressed air chamber into communication, through the other valve element of said last mentioned valve means, with said second combustion chamber.

5. A starting device according to claim 1 wherein said first means include an air compressor,

a first compressed air chamber,

pipe means for connecting the delivery of said compressor with said first compressed air chamber,

a first check valve in said last mentioned pipe means opening toward said first compressed air chamber,

a distributing device having an inlet and an outlet, said inlet communicating with said first compressed air chamber, said distributing device being adapted to occupy either of two positions thereof to wit 'an opening one, in which its inlet is in communication with its outlet and a closing one in which its inlet and its outlet are cut ofif from each other,

two pipes, a first one and a second one, the first one communicating with the outlet of said distributing device and the second one communicating with the first one, I

said first pipe leading to said first combustion chamher,

a second check valve in said first pipe opening toward said first combustion chamber,

a third pipe extending from said second combustion chamber to an outlet adapted to communicate with the atmosphere,

a third check valve in said third pipe adapted to open toward said second combustion chamber, and

a pneumatic device operative by compressed air from said second pipe for opening said last mentioned check valve,

said second means including a second compressed air chamber, said first and second compressed air chambers being portions, in line with each other, of the inside of a cylinder, with a partition piston dividing into inside of said cylinder into said two compressed air chambers, and an abutment rigid with said cylinder being adapted to cooperate with said partition piston to limit the volume of said first compressed air chamber to a value several times smaller than the volume of said second com-' pressed air chamber,

a fourth check valve in said partition piston opening fbrom said first to said second compressed air chamers,

means, including a conduit extending longitudinally from the end of said second compressed air chamber opposed to that adjoining said first compressed air chamber and said third pipe, which opens transversely into said conduit, for connecting said second compressed air chamberwith said engine second combustion chamber, I

a fifth check valve operatively connected with said partition piston for controlling the communication between said longitudinal conduit and said second compressed air chamber, said fifth check valve opening toward the inside of said second compressed air chamber,

a slide valve in said longitudinal conduit adapted to place said third pipe in communication with the atmosphere when said fifth check valve is closed and with said longitudinal conduit when said fifth check valve is open, and

resilient means for urging said slide valve toward the. position thereof where it places said third pipe in communication with the atmosphere.

-6. A starting device according to claim 5 further coma prising a discharge pipe and, between said compressor and said first compressed air chamber, a pneumatic disconnector adapted, when the pressure in said first compressed air chamber reaches a predetermined limit, to dis@ connect said compressor from said first compressed air chamber and to connect said compressor with said discharge pipe.

7. A starting device according to claim 6 wherein said pneumatic disconnector comprises a casing forming three successive compartments,

the first of said compartment being connected with the upstream end of the pipe means for connecting the delivery of said compressor with said first compressed air chamber,

the second of said compartments being connected with said discharge pipe,

the third of said compartment being connected with the downstream end of the above mentioned pipe means,

pipe means for connecting the first and third of said compartments together,

first check valve means in said last mentioned pipe means opening toward said third compartment,

said first and second compartments being connected together by a passage,

second check valve means in said passage opening toward said first compartment,

spring means resiliently opposing the opening of said second check valve means,

said second compartment being in the form of a cylinder,

a piston slidable in said second compartment adapted to cooperate with said second check valve means for opening it against the action of said last mentioned spring means,

said second and third compartments being connected together by a passage,

third check valve means in said last mentioned passage opening toward the portion of said second compartment located on the other side of said last mentioned piston from said second check valve means,

said third compartment including a cylindrical portion,

a piston slidable in said cylindrical portion of said third compartment, and

spring means for resiliently opposing the thrust on said last mentioned piston of the pressure in said first compressed air chamber.

8. A starting device according to claim wherein said compressor belongs to a motor-compressor system, which starting device comprises a control device including a movable control member for starting said motor-compressor unit, means operative by said control member for operating said distributing device and means for automatically restoring said control member into the position thereof for which said motor-compressor unit is stopped.

9. A starting device according to claim 8 comprising a discharge pipe provided with a discharge orifice, said discharge orifice being normally connected with the output of said air compressor,

a fixed valve seat,

valve means adapted to cooperate with said valve seat and operatively connected with said control member for cutting off said air compressor output from said discharge orifice,

spring means urging said last mentioned valve means toward the closing position thereof,

said last mentioned valve means being responsive to the opposed actions of the pressure in said discharge pipe tending to open it and of said last mentioned spring means tending to close it, the force of said last mentioned spring means being lower than the effect thereon of the pressure in said discharge pipe,

pneumatic means for operating said distributing device,

and

a transmission pipe extending between said pneumatic means and said discharge pipe upstream of said last mentioned valve means.

10. A starting device according to claim 9 wherein said control member is rigid with a piston,

a cylinder adapted to cooperate with said last mentioned piston,

cooperating resilient locking means between said last mentioned piston and cylinder for resiliently holding said piston driven in said cylinder, said resilient locking means being arranged to yield when, after opening of said last mentioned valve means, said last mentioned piston is subjected to the pressure of air from said compressor, said last mentioned piston being adapted, when driven out by said pressure, to clear the orifice of said discharge pipe.

11. A starting device according to claim 5 comprising a movable control member adapted to occupy an operative position and an inactive position,

an electric motor for driving said air compressor,

a discharge pipe provided with a discharge orifice, said discharge orifice being normally connected with the output of said air compressor,

a fixed valve seat,

valve means adapted to cooperate with said valve seat and operatively connected with said control member for cutting oit said air compressor output from said discharge orifice,

spring means urging said last mentioned valve means toward the closing position thereof,

said last mentioned valve means being responsive to the opposed actions of the pressure in said discharge pipe tending to open it and of said last mentioned spring means tending to close it, the force of said last mentioned spring means being lower than the efiect thereon of the pressure in said discharge pipe,

means for resiliently urging said distributing device toward the closing position thereof,

pneumatic means for bringing said distributing device into opening position against the action of said resiliently urging means,

a pipe extending between said pneumatic means and said discharge pipe upstream of said last mentioned valve means, and

an electric circuit for said electric motor, said electric circuit including a fixed contact rigid with said fixed valve seat and a movable contact rigid with said control member adapted to cooperate with said fixed contact, said fixed and movable contacts being resiliently to lock in each other.

12. A starting device according to claim 9 wherein said pneumatic device includes a cylinder having one end thereof connected with said transmission pipe,

a check valve in said transmission pipe opening toward said last mentioned cylinder,

a leak passage in shunt with said transmission pipe across said check valve,

a piston in said last mentioned cylinder, and

means for resiliently urging said last mentioned piston toward said last mentioned check valve.

References Cited UNITED STATES PATENTS 3,149,773 9/1964 Cudaby 123-46 WENDELL E. BURNS, Primary Examiner. 

1. IN AN INTERNAL COMBUSTION ENGINE INCLUDING A CYLINDER, A SINGLE PISTON FREELY SLIDABLE IN SAID CYLINDER DIVIDING IT INTO TWO VARIABLE VOLUME COMBUSTION CHAMBERS, A FIRST ONE AND A SECOND ONE, SAID CYLINDER BEING PROVIDED WITH DISCHARGE PORTS TO BE CLEARED BY SAID PISTON WHEN THE VOLUME OF EACH OF SAID COMBUSTION CHAMBERS IS MAXIMUM, A STARTING DEVICE WHICH COMPRISES, IN COMBINATION, FIRST MEANS FOR FEEDING AIR UNDER PRESSURE INTO THE FIRST COMBUSTION CHAMBER FOR CONNECTING THE SECOND COMBUSTION CHAMBER WITH THE ATMOSPHERE, WHEREBY SAID PISTON IS PUSHED IN THE DIRECTION FROM SAID FIRST COMBUSTION CHAMBER TOWARD SAID SECOND COMBUSTION CHAMBER INTO THE POSITION THEREOF FOR WHICH SAID FIRST COMBUSTION CHAMBER HAS ITS MAXIMUN VOLUME, AND 